Various cardiovascular procedures, such as angioplasty and stent placement, among others, are performed by inserting into and manipulating within a patient's vasculature, wires and catheters adapted to perform those procedures. In coronary and other such intravascular interventional procedures access to the vasculature typically is percutaneous, often through the femoral artery, involving insertion of a needle in the region of the groin to form a track through subcutaneous tissue and to puncture and create an arteriotomy in the artery. A guide wire then is advanced through the needle and into the femoral artery. The needle then is removed and a dilator carrying an introducer sheath then is advanced over the guidewire, along the needle track and into the femoral artery. The dilator enlarges the track through the tissue and widens a puncture in the vessel so that it may receive the introducer sheath, subsequent catheters and the like. With the introducer sheath having been advanced into the vessel, the dilator is removed leaving the introducer sheath in place. The guidewire and introducer sheath serve as guides to provide access into the femoral artery, through the arteriotomy, for catheters or other instrumentalities in order to perform the selected procedure within the patient's vasculature.
After the intravascular procedure has been, completed, the procedural devices are removed and the arteriotomy must be closed. A number of techniques are known to facilitate closure and healing of the arteriotomy. These include application of pressure at the puncture site, often for a relatively extended length of time until hemostasis is self-sustaining, or the use of biological adhesives or plugs adapted to seal the arteriotomy, or the use of staples or clips. Some closure systems include a patch in an external position covering the arteriotomy and connected by a suture that extends through the puncture to an internal anchor element that spans the opening. Some closure systems include an arrangement to engage the artery to temporarily draw the edges of the arteriotomy together while a filial closure device, such as a staple, sutures, adhesives or other means may be used to effect the permanent closure of the arteriotomy. Some closure systems include a tubular guiding sheath that is percutaneously positioned through the enlarged needle track with a distal outlet opening of the guiding sheath disposed immediately adjacent the arteriotomy. With the sheaths so positioned, closure device can be advanced through the sheath to apply its closure element or procedure to the region of the arteriotomy to close it. In order for such a sheath-based system to be effective, it is important that the distal end of the sheath be stabilized in a fixed position relative to the vascular puncture. After the closure device has performed its function and hemostasis has been achieved, the sheath and other elements of the closure system are removed.
A challenge associated with most known vascular closure devices (VCDs) is locating the exterior surface of the vessel wail and distinguishing that surface from the surrounding subcutaneous tissue so that the closure device can be applied accurately with respect to that exterior surface. Errors in accurately determining the exterior surface of the vessel wall can result in hematoma if the VCD is deployed too far away from the vessel wall, or can result in embolization if the VCD is unintentionally deployed within the vessel lumen. It would be desirable to provide a system that can promptly and effectively achieve permanent hemostasis at a percutaneous vascular puncture without requiring the clinician to accurately locate the exterior surface of the vessel wall at an arteriotomy.